THE HISTORY OF A DOCTRINE. 



215 



These two great men, then, each looked around in the then 

 darkness as far as his light carried him. All beyond that was 

 chance to each ; and Fate willed that Newton, whose light shone 

 further than his rival's, found it extend just far enough to show 

 the entrance to the wrong way. He reaches the conclusion that 

 we all know ; and with the result on other men's thought that, 

 light being conceded to be material, heat, if af&liated to light, 

 must be regarded as material too, for we may see this strange 

 conclusion drawn from experiments of Herschel a century later. 



It would seem that the result of this unhappy corpuscular 

 theory was more far-reaching than we commonly suppose, and 

 that it is hardly too much to say that the whole promising move- 

 ment of that age toward the true doctrine of radiant energy is not 

 only arrested by it, but turned the other way ; so that in this re- 

 spect the philosophy of fifty years later is actually further from 

 the truth than that of Newton's predecessors. 



The immense repute of Newton as a leader, on the whole so 

 rightly earned, here leads astray others than his conscious disci- 

 ples, and, it seems to me, affects men's opinions on topics which 

 appear at first far removed from those he discussed. The adop- 

 tion of phlogiston was, as we may reasonably infer, facilitated by 

 it, and remotely Newton is, perhaps, also responsible in part for 

 the doctrine of caloric a hundred years later. After him, at any 

 rate, there is a great backward movement. We have a distinct 

 retrogression from the ideas of Bacon and Hobbes and Boyle. 

 Night settles in again on our subject almost as thick as in the 

 days of the school-men, and there seems to be hardly an important 

 contribution to our knowledge, in the first part of the eighteenth 

 century, due to a physicist. 



" Physics, beware of metaphysics," said Newton — words which 

 physicists are apt so exclusively to quote, that it seems only due 

 to candor to observe that the most important step, perhaps, in the 

 fifty years which followed the "Optics," came from Berkeley, 

 who, reasoning as a metaphysician, gave us during Newton's life- 

 time a conception wonderfully in advance of his age. Yet the 

 " New Theory of Vision " was generally viewed by contemporary 

 philosophers as only an amusing paradox, while " coxcombs van- 

 quish [ed] Berkeley with a grin" ; and this contribution to science 

 — an exceptional if not a unique instance of a great physical gen- 

 eralization reached by a priori reasoning — though published in 

 1709, remains in advance of the popular knowledge even in these 

 closing years of the nineteenth century. 



In the mean time a new error had risen among men — a new 

 truth, as it seemed to them, and a thing destined to have a strong 

 reflex action on the doctrine of radiant energy. It began with the 

 generalization of a large class of phenomena (which we now asso- 



